Teach BaseIndexOffset::match to identify base pointers in loops.
The small utility function that pattern matches Base + Index +
Offset patterns for loads and stores fails to recognize the base
pointer for loads/stores from/into an array at offset 0 inside a
loop. As a result DAGCombiner::MergeConsecutiveStores was not able
to merge all stores.
This commit fixes the issue by adding an additional pattern match
and also a test case.
Reviewer: Nadav
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188936 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ba23aac..bbea113 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7859,17 +7859,29 @@
static BaseIndexOffset match(SDValue Ptr) {
bool IsIndexSignExt = false;
- // Just Base or possibly anything else.
+ // We only can pattern match BASE + INDEX + OFFSET. If Ptr is not an ADD
+ // instruction, then it could be just the BASE or everything else we don't
+ // know how to handle. Just use Ptr as BASE and give up.
if (Ptr->getOpcode() != ISD::ADD)
return BaseIndexOffset(Ptr, SDValue(), 0, IsIndexSignExt);
- // Base + offset.
+ // We know that we have at least an ADD instruction. Try to pattern match
+ // the simple case of BASE + OFFSET.
if (isa<ConstantSDNode>(Ptr->getOperand(1))) {
int64_t Offset = cast<ConstantSDNode>(Ptr->getOperand(1))->getSExtValue();
return BaseIndexOffset(Ptr->getOperand(0), SDValue(), Offset,
IsIndexSignExt);
}
+ // Inside a loop the current BASE pointer is calculated using an ADD and a
+ // MUL insruction. In this case Ptr is the actual BASE pointer.
+ // (i64 add (i64 %array_ptr)
+ // (i64 mul (i64 %induction_var)
+ // (i64 %element_size)))
+ if (Ptr->getOperand(1)->getOpcode() == ISD::MUL) {
+ return BaseIndexOffset(Ptr, SDValue(), 0, IsIndexSignExt);
+ }
+
// Look at Base + Index + Offset cases.
SDValue Base = Ptr->getOperand(0);
SDValue IndexOffset = Ptr->getOperand(1);